The present invention relates to an improved apparatus for manufacturing form-fitting insoles.
A process for manufacturing form-fitting insoles is already known; it is disclosed in Italian patent no. 1,124,338 dated Oct. 9, 1979 and entails the following operating steps:
placing a parallelepiped made of a fibrous spongy load-deformable material at the bottom of each one of a pair of adjacent trays that extend from a single structure; PA1 pouring into the trays a preparation that impregnates the spongy fibrous material and reacts, by foaming, in a sufficiently short time; PA1 covering the trays and the above described components with a double-stretch piece of fabric treated so as to be impermeable, which is kept stretched by an appropriate frame; PA1 placing the user's feet on the fabric inside the trays, so as to deform both the fabric and the fibrous spongy material; PA1 waiting through the reaction time of the preparation, so that the produced shape remains subsequently unchanged; PA1 removing the unfinished products thus obtained and trimming them so as to leave only the impression of the sole of the foot, adapting it to the shoe in which it is to be inserted.
Although this method is technically very valid, also in view of the state of the art prior to its invention, it has been found to be limited in its potential by the means used to execute it.
The two trays in fact extend from a single structure and are therefore rigidly coupled to each other, forcing the user to place his feet parallel to each other, totally altering the normal standing position in which, depending on the individual person, the toes diverge by a greater or smaller extent according to a so-called abduction angle.
Placing one's feet in the trays in an unnatural position generates tensions that deform the sole of the foot, so that the impression can assume an incorrect shape.
Another limitation to the process described above is due to the apparatus and is constituted by the co-planar arrangement of the two trays.
It is in fact known that in a person whose legs are abnormally long or short or have different lengths, the upright posture causes a series of skeletal and postural adjustments (deviations, torsions, flexions, etcetera) which are aimed at compensating for the abnormality to achieve satisfactory equilibrium.
This naturally also affects the shape of the sole of the feet (and the different position of one with respect to the other), and the execution of the process with co-planar trays makes it impossible to produce a physiologically correct impression that is capable of making the person maintain a posture that compensates for the abnormality.